Automatic axial pressure device applicable to friction drives



Feb. 12, 1952 F PERRUCA 2,585,830

AUTOMATIC AXIAL. PRESSURE DEVICE APPLICABLE TO FRICTION DRIVES FiledFeb. 4, 1948 2 SHEETS-SHEET l lilillll .ZvveNra/ EL/; fiance-van a: WHall, $bd

Feb. 12, 1952 F. PERRUCA 2,585,830

Aggi AXIAL PRESSURE DEVICE AUTOM APPLI E TO FRICTION DRIVES Filed Feb.4, 1948 w 2 SHEETSSHEET 2 Patented Feb. 12, 1952 T T F F I C E AUTOMATICAXIAL PRESSURE DEVICE APPLICABLE TO FRICTION DRIVES Felix Perruca,Saint-EtiennaFrance, assignor to Socrete des Fabrications Unicurn,Paris,

France Application February 4, 1948, Serial No. 6,185 In France February8, 1947 The subject of this invention is an automatic axial pressuredevice, especially intended to be applied to mechanisms for transmittingpower by friction, such as variable ratio friction drives. In suchdrives the power has been transmitted from a driving shaft to a drivenshaft by smooth balls or rollers interposed between, and in rollingfrictional contact with, substantially disc-shaped members secured to,and rotating with, the said shafts. The power transmitted by such adrive is a function of the axial pressure between the said members andthe said balls or rollers. EX- cessive pressure will cause unduestresses and wear of these parts, while insuflicient pressure willresult in a reduction of the power transmitted.

The purpose of the present invention is to provide means forautomatically maintaining this pressure at its optimum value, i. e. atthe lowest value consistent with the transmission, to the driven shaft,of the torque required.

According to the present invention a means for automatically varying theaxial pressure between the rotating members of mechanisms fortransmitting torque by friction, e. g. variable ratio friction drives,comprises a device, adapted to vary the said pressure directly as thetorque transmitted, interposed between a friction-driven member and theshaft to which said member is normally secured.

For a more ready comprehension of the present invention reference may behad to the accompanying drawings, which,'however, are given by way ofexample and are not intended to constitute any limitation, and in which:

' Figure l is a general view, in elevation and in part section, of avariable ratio friction'drive equipped with the axial pressure device;

Figure 2 shows on a larger scale a sectional view of the axial pressuredevice applied to the driven shaft;

Figure 3 is a detailed radial sectional view of the device with theannuli in the spaced out position;

Figure 4 shows on a larger scale a radial sectional view of the devicewith the annuli in the minimum spaced position;

Figure 5 is an enlarged plan view of the special grooves which serve asrunways for the balls interposed between the annuli, and

Figure 6 is an enlarged elevational and sectional view along the circleof radius R, showing the axial displacement of a ball resulting from itscircular displacement in its supporting groove.

In the embodiment illustrated inFigures- 1 and 2 Claims. (01. 74-208) 2of the accompanying drawings, the device'is shown applied to a variableratio friction drive. A driving shaft I is geared via pinions 2 to'theshafts 3', said shafts 3' each having secured to the end of saidshaft remote from the shaft I a substantially disc-shaped member 3. Thecircular faces of the said members 3 are co-planar. A driven shaft 10has secured to it a further substantially disc-shaped member 5, thecircular face of. said member opposed to the members 3 lying in a planeparallel to the said plane through the circular faces of the members 3.

Interposed between the member 5 and the members 3 and in rollingfrictional contact with the said members are two smooth rollers 4 havingchamfered annular faces it which make the said rolling frictionalcontact. The rollers 4 are supported for free rotation on spindlessecured to brackets I9, the said brackets being adapted to move the saidrollers symmetrically across the faces of the said members 3 and 5,thereby varying the speed ratio of the driving shaft l to the drivenshaft 1.0.

Since the foregoing is well known in the art and forms no part of thepresent invention, per s-e, it is not proposed to describe it in furtherdetail.

The new device comprises essentially two like annuli l and 8, one ofwhich, i, is secured coaxially to the said driven member 5, and theother, 8, secured co-axiallytoa further member IS, the said member l6abutting against one end of a helical spring 15, the other end of saidhereinafterv described in detail, co-operating with the said balls. Theshaft ill has a co-axial cylindrical recess into which the said memberI6 is journalled, the member !5 having a co-a-xial spigot 6 journalledin to the member 5, said member 16 being constrained to rotate with saidshaft by a key 20 (see Figure 1).

The annulus 'iis secured to the member 5 by anyknown means, indicatedgenerally at l! in Figure 2; Q

The annulus 8 is a snug fit about the base of the spigot 6 and issecured to the member it by means generally indicated at 9 (Figure 2).In the end of the member it remote from the said spigot is a co-axialcylindrical ,recess in which is disposed ahelical spring 15 of squaresection-adapted to urge the saidmeinber liain an axial direction, thusapplying axial pressure, through the medium of the annulus 8, balls 1and annulus 1, to the member 5.

When torque is applied to the member 5 the said member turns through afraction of a revolution on the spigot 6, rotating the annulus I securedto the said member 5 with respect to the annulus 8 secured to the saidmember l5, said member It being constrained to rotate with the shaft [0by the key 20 hereinbefore described. The grooves 22 are so constructedthat relative rotation of the annuli forces the balls against inclinedsurfaces of the said grooves thus forcing the annuli apart. Thismovement is yieldingly opposed by the spring l5, hence the effect ofapplying increasing torque to the member 5 is to increase the axialpressure urging the said member against the smooth rollers 4, therebyincreasing the friction between the said rollers 4 and the members 3 and5, and hence the torque that can be transmitted.

A stop is provided, comprising an axially disposed rod I4 withhemispherical ends, one of which is seated in an axial depression in themember Hi, the other end of said rod seating in a similar depression inthe end of the screw I3. The screw I3 has a coarse pitch thread and isdisposed in an axial correspondingly threaded hole in the shaft Ill. Thesaid hole extends axially to the end of the said shaft remote from themember 5 where the said hole is threaded to co-operate with the threadsof a screw plug II. A torsion spring [2 is secured by one end to theplug l l and by the other end to the screw 13 and is adapted to urge thesaid screw and hence the rod [4 against the member [6.

A steady increase in torque will feed the member l6 against the stopwith considerable force and the screw [3 by virtue of its coarse thread,will be urged away from said member relatively slowly, against theaction of the spring l2. An increase of torque of short duration,however, will not affect the stop. The action of the stop 14 is tominimize movement of the member l6 and resulting changes of axialpressure on the member 5 consequent upon fluctuations in torque of shortduration.

The grooves 22 are of definite contour and are disposedcircumferentially adjacent each other (Figure 5). The said contour isderived as follows:

(1) In radial cross-section the groove isa secant of a circle of thesame radius (1 as the balls used therewith.

(2) In vertical cross-section along the cir- I cumference of the circleradius R (Figure 5) the groove is a secant of a circle of large radius(r) compared with the radius of the said balls. The fulfilment of thesetwo conditions defines grooves 22 as shown in Figure 5.

It can be seen that if two axially opposed discs or annuli bearing ontheir opposed faces like sets of grooves constructed as described above,having a smooth ball interposed between each pair of opposed grooves,are slightly roi1;

4 consequent axial displacement thereby increasing the axial pressure onthe said member.

I claim:

1. In a mechanism including rotary members for transmitting torque byfriction under variable ratio drives, the provision of means forautomatically varying the axial pressure between said rotary members andincluding two axially opposed annuli adapted to rotate in unison withthe corresponding rotary member and having on their opposed circularfaces like sets of circumferentially interengaging segmental grooves thelongitudinal axis of which forms a circle round the axis of said annuli,the radial cross-section of the successive grooves forming secantshaving a predetermined radius and the chord of which is reducedgradually from a maximum at the center of each segmental groove towardsa minimum at the cooperating ends of two successive segmental grooves,the outline of each groove along the medial longitudinal cross-sectionthereof corresponding when developed to the arc of a circle ofpredetermined radius, and a ball enclosed between each couple ofcooperating grooves and the diameter of which is equal to that of thesecants forming the cross-section of the latter, the angular shifting ofthe two annuli with reference to one another producing their axialspacing according to the amplitude of movements of the balls out oftheir position in register with the central portion of the cooperatinggrooves and a cage containing said balls and a yielding adjustable stoparrangement ior automatically compensating the clearance due to wearbetween the annuli and balls including a driven member provided with anaxial bore tapped at both ends, means yieldingly urging said drivenmember and corresponding annulus apart, a threaded plug engaging theouter tapped end of said bore, a coil spring one end of which is securedto said plug, a threaded member to which the other end of the spring issecured, screwed inside the inner tapped end of the bore above mentionedand a stop adapted to be urged by the threaded member against theannulus last mentioned.

2. In a mechanism including rotary members for transmitting torque byfriction under variable ratio drives, the provision of means forautomatically varying the axial pressure between said rotary members andincluding two axially opposed annuli adapted to rotate in unison withthe corresponding rotary member and having on their opposed circularfaces like sets of circumferentially interengaging segmental grooves thelongitudinal axis of which forms a circle round the axis of said annuli,the radial cross-section of the successive grooves forming secantshaving a predetermined radius and the chord of which is reducedgradually from a maximum at the center of each segmental groove towardsa minimum at the cooperating ends of two successive segmental grooves,the outline of the groove along the medial longitudinal cross-sectionthereof corresponding when developed to the arc of a circle ofpredetermined radius, and a ball enclosed between each couple ofcooperating grooves and the diameter of which is equal to that of thesecant forming the cross-section of the latter, the angular shifting ofthe two annuli with reference to one another producing their axialspacing according to the amplitude of movements of the balls out oftheir position in register with the central portion of the cooperatinggrooves and a cage containing said balls and a yielding adjustable stoparrangement for automatically compensating the clearance due to wearbetween the annuli and balls including a driven member provided with anaxial bore tapped at both ends, means yieldingly urging said drivenmember and corresponding annulus apart, a recess being provided axiallyof last mentioned annulus facing said driven member, a threaded plugengaging the outer tapped end of said bore, a coil spring one end ofwhich is secured to said plug, a threaded member to which the other endof the spring is secured, screwed inside the inner tapped end of thebore above mentioned and provided with a recess at the end opposed tothe spring, and an elongated stop member the ends of which engagerespectively the recesses in the threaded member and annulus.

FELIX PERRUCA.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 20,801 Gove et al. July 19,1938 1,585,140 Erban May 18, 1926 1,683,715 Erban Sept. 11, 19281,833,475 Standish Nov. 24, 1931 2,100,632 Chilton Nov. 30, 19372,123,007 Hayes July 5, 1938 2,123,008 Hayes July 5, 1938 2,132,801Perruca Oct. 11, 1938 2,445,066 Hayes July 13, 1948 FOREIGN PATENTSNumber Country Date 615,063 Great Britain Dec. 31, 1948

